Strengthens abdominal muscles. Lie on the floor with your knees bent, feet flat on the floor. Link your hands loosely behind your head with your elbows wide. Breathe in and slowly contract your abdominal muscles as you exhale, lifting your head and shoulders off the floor; then lower back to the floor. Repeat 30 times. Next, drop your knees to the right side and do 30 more. Repeat on the left side.